1. Field of the Invention
This invention is directed to a replaceable rotating workpiece spindle with normally closed collet, particularly for multiple spindle machines where the workpiece carrying spindles are individually rotated and are indexed to work stations where work is performed on the workpiece.
2. Description of the Prior Art
Machine tools in which there are multiple spindles indexed from one position to another are well-known. A workpiece is carried on each of the spindles and is indexed from a loading position through a series of work stations to an unloading position. In some cases, the work is roated while the tools are held stationary, while in some machines the opposite is true.
When rotating workpiece-carrying spindles are employed, the prior machinery has been limited in its accuracy capabilities because it lacks suitable adjustment of spindle positioning and also lacks the capability of automatically holding the workpiece collet in the proper position with respect to a reference position to which the tooling could be set. Without accurate repetitive positioning of the collet with respect to a reference plane, tooling cannot accurately operate on a workpiece held therein.
Additionally, a problem has arisen in such multiple spindle machine tools because the spindle drive belt has a tendency toward excessive wear due to engagement of the spindle by the moving belt, with a substantial velocity difference, to cause excessive belt wear. Thus, prior equipment has not reached optimum accuracy and has needed extra adjustment due to belt wear.